I came across this post on the boards concerning using the jQuery BlockUI plugin, which was handy because I hadn’t had any exposure to the plugin previously.  BlockUI is very handy way of controlling your interface to avoid unwanted user behavior.  For instance, if you’re sending a JavaScript Remoting call over the wire which might take a decent amount of time to process on the Apex side, you could use BlockUI to grey out the page and display a message like this:

Here’s some baseline code which would show a brief message like that one when quicksaving a record:

I would recommend downloading the plugin and serving it from a static resource, however, to avoid any “non-secure content on a secure page” type browser warning. BlockUI has a lot of different options to it and several templates of displaying error messages. Let us know how you might use it for your project.